1. Field of the Invention
The present invention relates to the improved production or yield of tertiary amyl methyl ether (TAME) and/or tertiary amyl alcohol (TAA) from predominantly C.sub.5 hydrocarbon feed streams containing mixed C.sub.5 olefins which are of relatively low value.
2.Description of Prior Art
Various methods are known in the art for the conversion of branched olefins to the corresponding ether and/or alcohol. See U.S. Pat. Nos. 4,605,787, 4,575,566, 4,925,455, 4,957,709, 4,962,239, 4,967,020, 4,969,987, 4,830,685, 4,835,329, 4,827,045, 4,826,507, 4,814,519, 5,001,292, 5,003,112 and the like.
Likewise, methods are known whereby linear olefins can be converted by skeletal isomerization to branched olefins See, for example, U.S. Pat. Nos. 4,037,029, 4,793,984, 4,683,217, 4,973,785, 4,882,038, 4,758,419, 4,500,651, 4,973,460 and the like.
Various integrated processes for the conversion of hydrocarbons to gasoline components which involve etherification of branched tertiary C.sub.4 and/or C5 olefins are also known. See, for example, U.S. Pat. Nos. 4,988,366, 4,925,455, 4,957,709, 4,969,987, 4,830,635, 4,835,329, 4,827,045, 4,826,507, 4,854,939, 5,001,292, 4,857,667, 5,009,859, 5,015,782, 5,013,329 and the like.
European publication 0 026,041 describes a process for producing olefins and/or ethers of high octane number from a wide C.sub.2 to C.sub.10 olefinic stream .The wide olefinic feedstock is restructured over a zeolite catalyst to form primarily C.sub.4 to C.sub.7 olefins, the C.sub.4 to C.sub.7 iso-olefins are reacted with methanol to form high octane ethers and unreacted olefins and methanol are separated from the ether product and recycled to the restructuring operation.
U.S. Pat. No. 4,814,519 shows a two-stage process for the production of ethers from olefin-containing feedstock such as from an FCC unit whereby the feedstock is reacted under conditions to maximize production of C.sub.4 -C.sub.5 iso-olefins, particularly tertiary iso-olefins. The resulting iso-olefin rich product is then subjected to a catalytic etherification reaction to produce ethers such as TAME.
The above art teaches that the amount of ether which can be produced from a mixed olefin stream is limited to the contained branched olefins and that the amount of contained branched olefins in the stream is limited by the thermodynamic equilibrium condition of this source olefin stream.
The current invention provides a process whereby substantially all of the contained olefin in the feed stream can be upgraded to TAME.